A cocrystal of 3α-hy­droxy­tirucalla-8,24-dien-21-oic acid and 3β-fluoro­tirucalla-7,24-dien-21-oic acid (0.897:0.103)

S Yousuf; R S T Kamdem; P Wafo; B T Ngadjui; Hoong-Kun Fun

doi:10.1107/S1600536811011159

. 2011 Mar 31;67(Pt 4):o1015–o1016. doi: 10.1107/S1600536811011159

A cocrystal of 3α-hydroxytirucalla-8,24-dien-21-oic acid and 3β-fluorotirucalla-7,24-dien-21-oic acid (0.897:0.103)

S Yousuf ^a, R S T Kamdem ^b, P Wafo ^b, B T Ngadjui ^c, Hoong-Kun Fun ^d,^*,^‡

PMCID: PMC3099936 PMID: 21754032

Abstract

The title compound, 0.897C₃₀H₄₈O₃.0.103C₃₀H₄₇O₂F is a co-crystal of two triterpenes isolated from the resin of Canarium schweinfurthiiand Engl. Both triterpenes consists of four trans-fused rings having chair/half-chair/half-chair and envelope conformations. The molecular conformations are stabilized by intramolecular C—H⋯O hydrogen bonds, forming rings of S(7) graph-set motif. In the crystal, molecules are linked by intermolecular O—H⋯O and C—H⋯O interactions, forming sheets parallel to (001). All atoms. excepting the axially-oriented hydroxyl group in the major component and the equatorially-oriented fluorine atom in the minor component, are overlapping.

Related literature

For the crystal structure of 3α-hydroxytirucalla-7,24-diene-21-oic acid, see: Mora et al. (2001 ▶). For the crystal structure of 3α-hydroxytirucalla-8,24-diene-21-oic acid, see: Yousuf et al. (2011 ▶). For the biological activity of canarium schweinfurthiiand, see: Atawodi (2010) ▶; Dongmo et al. (2010 ▶). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ▶). graphic file with name e-67-o1015-scheme1.jpg

Experimental

Crystal data

0.897C₃₀H₄₈O₃·0.103C₃₀H₄₇O₂F
M _r = 455.88
Trigonal,
a = 11.2868 (9) Å
c = 36.446 (3) Å
V = 4020.9 (5) Å³
Z = 6
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 100 K
0.29 × 0.24 × 0.13 mm

Data collection

Bruker SMART APEXII DUO CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009) ▶ T _min = 0.980, T _max = 0.991
27808 measured reflections
4454 independent reflections
4347 reflections with I > 2σ(I)
R _int = 0.105

Refinement

R[F ² > 2σ(F ²)] = 0.058
wR(F ²) = 0.153
S = 1.18
4454 reflections
316 parameters
H-atom parameters constrained
Δρ_max = 0.39 e Å⁻³
Δρ_min = −0.33 e Å⁻³

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811011159/rz2572sup1.cif

e-67-o1015-sup1.cif^{(29KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811011159/rz2572Isup2.hkl

e-67-o1015-Isup2.hkl^{(218.3KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1O1⋯O2ⁱ	0.87	1.81	2.654 (3)	165
O3—H3A⋯O2ⁱⁱ	0.84	2.04	2.818 (4)	154
C12—H12B⋯O1	0.99	2.56	3.262 (4)	128
C22—H22A⋯O3ⁱⁱⁱ	0.99	2.40	3.300 (5)	151

Open in a new tab

Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

RSTK thanks the H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, for providing research facilities. SY thanks the School of Physics, Universiti Sains Malaysia, for providing X-ray diffraction research facilities. HKF thanks the Malaysian Government and Universiti Sains Malaysia for the Research University Grant No. 1001/PFIZIK/811160.

supplementary crystallographic information

Comment

The title compound is a co-crystal of two triterpenes namely 3α-hydroxytirucalla-7,24-dien-21-oic acid (or epielemadienolic acid, I) as a major component (89.7%) and 3β-fluorotirucalla- 7,24-dien-21-oic acid (II) as minor component (10.3%). The co-crystal was isolated during the phytochemical investigation of the dichloromethane soluble part of the resins of the medicinally important plant Canarium schweinfurthii of Cameroon. The plant has been used for the treatment of a wide range of ailments including malaria, fever and diarrhea (Atawodi, 2010; Dongmo et al., 2010). The refinement of the crystal structure revealed I and II as major (89.7%) and minor (10.3%) component, respectively with the difference that in II the axially oriented hydroxyl group attached to C3 has been replaced by the equatorially oriented fluorine atom. The asymmetric unit of the co-crystal (Fig. 1) consists of the mixture of I (Fig. 2) and II (Fig. 3). The crystal structure of the major component I has already been reported and the space group (P3₁21) and cell parameters were found to be similar to those previously reported (Mora et al.. 2001, Yousuf et al., 2011). However the minor component II was found to be a new triterpene. In both components the molecular structure showed that the trans fused rings A/B/C and D adopt chair [Q= 0.550 (4) Å, θ = 7.1 (4)° and φ = 88 (3)°] / half-chair [Q= 0.530 (4) Å, θ = 49.5 (4)° and φ = 323.5 (6)°] / half-chair [Q= 0.652 (4) Å, θ = 100.4 (4)° and φ = 83.8 (3)°] and envelope [Q= 0.483 (2)Å and φ = 10.7 (4)°] conformations respectively. The chair and envelop conformations of rings C and D are stabilized by C12—H12B···O1 intramolecular hydrogen bond. In the crystal structure, the molecules are linked to form two-dimensional molecular sheets via O3—H3A···O2, O1—H1O1···O2 and C22—H22A···O3 intermolecular hydrogen bonds (symmetry codes as in Table 1) and arranged parallel to the (001) plane (Fig.2).The absolute configuration was assigned on the basis of our recently published triterpene crystal data (Yousuf et al., 2011).

Experimental

The resin (100 g) of Canarium schweinfurthii Engl. was collected in Yaounde, Cameroon, in May 2010 and identified by Professor Noumi, a botanist at the Department of Biology, University of Yaounde-1. A voucher specimen (HNC 25918.) was deposited at the National Herbarium of Cameroon in Yaounde. The resin (100 g) of C. schweinfurthii was allowed to dry under shade and extracted with dichloromethane. The extract (70 g) was subjected to column chromatography over silica gel (300 g, 60 × 5 cm) eluting with hexane followed by a mixture of n-hexane–EtOAc in order to increase polarity. The fractions eluted were monitored by thin layer chromatography and similar fractions were combined to give seven fraction FrA-FrG. Fraction FrA (200 mg), obtained on elution with a mixture of n-hexane-EtOAc (8:2 v/v), was subjected to further column chromatography over silica gel (70 g, 60 cm³ × 3, hexane-acetone equimolar solution) to yield crystals of the title compound. Recrystallization from n-hexane gave colourless crystals (60 mg).